1. Field of the Invention
The present invention relates to a permanent magnetic material, in particular to a Fe-lanthanoid-boron quenched permanent magnetic material and a permanent magnet made from the permanent magnet material.
2. Description of the Related Art
A Nd--Fe--B bonded magnet having excellent magnetic properties is commonly used in the field of compact and light weight magnets for use in electric products, cars and the like.
In U.S. Pat. No. 5,089,065, a permanent magnet is disclosed in which a ribbon-shaped thin film is formed by quenching a liquid mixture of five element components comprising Co and Y added Nd--Fe--B alloy, typically Nd.sub.15 Fe.sub.88 B.sub.7, the ribbon film is powdered, then the obtained powder is formed into a block (bulk-type metal magnet) using a nylon resin. The patent states that the magnetic energy of the quenched ribbon is more than 17 MGOe or 135 kJ/m.sup.3 in maximum energy product, (BH).sub.max. According to U.S. Pat. No. 5,089,065, the precipitation of the crystallite by the heat treatment of an amorphous alloy thin film is known, where Nd.sub.11 Fe.sub.72 CO.sub.8 B.sub.7.5 V.sub.1.5 is heat-treated at 650.degree. C. for 10 minutes and the maximum energy product (BH) max after heat treatment is 18 MGOe or 143 kJ/m.sup.3.
Japanese Patent Publication No. 3-52528 discloses a melt-quenched magnetic alloy having the composition of Nd.sub.0.1-0.5 (TM.sub.0.9-0.995 B.sub.0.005-0.1).sub.0.9-0.5, where TM represents a transition metal such as Fe, and an annealing method of the alloy after liquid-quenching in order to precipitate 20 to 400 nm of hard magnetic crystallite phases. The patent suggests that crystallite phase has a diameter less than the single magnetic domain, and (BH).sub.max of Nd.sub.0.15 (Fe.sub.0.95 B.sub.0.05).sub.0.85 reaches about 14 MGOe or 111 kJ/m.sup.3.
Permanent magnets have been investigated using Nd--Fe--B compositions having a lower Nd content than the above prior art references. For example, heat treatment of an amorphous ribbon having the composition of Nd.sub.4 Fe.sub.77 B.sub.19 is proposed by R. Coehoorn et al. (J. de Phys., C8, 1988, pp 669-670). However, the compound does not exhibit an acceptable Curie-point.
Furthermore, the improvement in magnetic properties by remaining amorphous phases in the ribbon and by using the remaining amorphous phase is not disclosed in the above Japanese Patent Publication No. 3-52528 and U.S. Pat. No. 5,089,065.
Although conventional Nd--Fe--B liquid,quenched magnets have high performance characteristics, the magnets are not competitive against ferrite magnets on the basis of price because the most suitable Nd content is over 10 atomic percent causing a high price. Therefore, the ferrite magnets are still generally used for motors, actuators and the like for medium-sized or larger-sized industrial machines. By the way, the general properties of the ferrite magnets, which range from 0.2 to 0.4 T for Br, 0.13 to 0.26 MA/m for Hc, and 7 to 36 kJ/m.sup.3 for (BH).sub.max, are significantly inferior to lanthanoid magnets. Under such circumstances, it is considered greatly significant to provide a magnet exhibiting the characteristics of Nd--Fe--B liquid-quenched magnet which are not as expensive as ferrite magnets, and which are acceptable for use in any common magnet applications.
Furthermore, the conventional Nd--Fe--B liquid-quenched magnets have been used as bonded magnets, and the powder cannot be directly bonded together without a resin binder due to poor formability. Thus, the conventional bonded magnets show poorer permanent magnetic characteristics due to the presence of the resin binder content.